I used to support MS Office products for a living, so I would like to offer a few suggestions that I did not yet see mentioned.

You are likely using a *.PST file to store your emails in Outlook. The problem is, is that these files corrupt really easily. But don't worry too much at this point, since you can often repair the damage by using scanpst.exe to repair the file. Make a backup first, then let the program inspect your file for errors. Even if your *.PST file is only a few months old, you will still often find it needs to be repaired. In addition to regularly backing up and repairing the *.PST file, you need to choose to compact the PST file when inside Outlook. If you do a search on how to compact the PST file from Microsoft's help pages, it will show you step by step.

The other common problem was that the Outlook profile itself would become corrupted, thus causing Outlook to run really slow. Create a new Outlook profile from the control panel and try that.

If this doesn't help, let me know. I will check this thread later tonight to see how you get on ..

Robert